The present invention generally relates to flexible circuits and more specifically to a strain relief for a flexible circuit connected between a movable assembly and a stationary component.
It is a problem in the field of flexible circuits to prevent bending the flexible circuit too sharply. A flexible circuit includes conductors or conductive traces between two flexible covers. The flexible covers are usually laminated to further protect the conductive traces. When the flexible circuit is bent too sharply, the layers on the outside of the bend are stretched and the layers on the inside of the bend are compressed.
Compression of the layers on the inside of the stressful bend can cause wrinkles in the lamination which may result in rippled conductors and delaminating of the cover on the inside of the stressful bend which may cause cracks in the flexible circuit. Delaminating or cracking of the cover on the inside of the stressful bend often leads to electrical circuit failure due to broken or fractured conductors within the flexible circuit. Stressful bend angles also cause the cover on the outside of the stressful bend to stretch which may lead to broken or fractured conductors or a torn cover.
Broken or fractured conductors are not easily detected by a visual inspection. Therefore, a failure may occur after a product has passed a visual inspection and is installed in the final assembly. Handling and vibration in final assembly can cause a flexible circuit having a stressful bend to be damaged leading to failure of the flex circuit.
Flexible circuits are used in a variety of designs wherein the flexible cable is routed from an initial position to an ending position to connect the two positions together. As the flexible cable is routed, the flexible cable may be bent around components, bent to interconnect two components together or may interconnect a moving component to a stationary component such as a printed circuit board. Movement of the moveable component may further bend the flexible cable to sharply, placing additional stress on the flexible cable at the location of the bend.
A typical data storage device includes a read/write head assembly for reading/writing data from/to a magnetic tape media as the magnetic tape media moves past the read/write head assembly. Data storage on tape media typically involves recording flux transitions in a series of narrow data tracks which are spaced closely together to maximize the amount of data that can be stored on a given length of tape media. To further maximize the amount of data that can be stored on the length of tape media, a plurality of parallel data tracks are recorded
During the recording process, the tape media is moved past the read/write head as flux transitions are imparted in a thin line referred to as a data track. The read/write head is controllably positioned by a servo system to read/write data from/to each next data track. As the read/write head assembly moves up and down, one end of the flexible cable interconnecting the read/write head assembly to the printed circuit board also moves up and down. Thus, the flexible circuit provides an electrical interconnect with minimal constraint on movement of the read/write head assembly.
A U-shaped flexible cable guide is disclosed by Butler, et al. (U.S. Pat. No. 5,953,183) for use with a data storage device having a head assembly that reads/writes data from a rotating disk. The combination of a U-shaped flexible circuit guide and a removable snap-fit pin restrain the flexible circuit in a position defined by an inner surface of the cable guide between the cable guide and the removable snap-fit pin. The U-shaped flexible circuit guide routes the flex circuit to an electrical component on the side of an actuator body to substantially restrain the flex circuit as the read/write head moves horizontally to read/write data from/to the rotating disk.
While the flex clamp disclosed in Butler restrains a flex circuit attached to a horizontally movable member, it fails to provide a method for restraining a flex circuit attached to a movable member that moves linearly up-and-down. Nor does Butler route the flex circuit away from the movable member and in the direction of a stationary component. Instead, Butler merely restrains the flex circuit that interconnects the movable member to the stationary component. Butler also fails to provide a method for routing and restraining more than one flex circuit such that the flex circuits transition through a controlled bend wherein the controlled bend allows the flex circuit to find its own natural relaxed position by use of gravity and the natural tendency of the flex circuit to want to lie flat. Instead, the flex circuit in Butler is positioned vertically on one edge such that the natural tendency of the flex circuit to lie flat will cause the flex circuit to fold creating two uncontrolled bends in the flex circuit and therefore creating two stressful bends which may cause damage to the flex circuit and therefore failure of the data storage device.
What is needed is a flex circuit strain relief for controlling the location and the angle of the flexible circuit bend in a manner that the allows the flex circuit to naturally roll in a relaxed position during movement of the movable member and to route and restrain more than one flex circuit simultaneously.
A flex circuit strain relief that routes and restrains multiple flex circuits that interconnect a movable component and a stationary component. One end of the flex circuit is connected to the movable component that moves linearly up-and-down. The flex circuit strain relief routes the flex circuit away from the movable component and reroutes the flex circuit in a second direction to create a natural bend in the flex circuit as the flex circuit is rerouted for connection to a stationary component. As the movable member moved linearly up-and-down, the natural bend of the flex circuit rolls with the movement to reduce the stress on the flex circuit during the movement.
The flex circuit strain relief includes a restraining member that attaches to the movable member and a corresponding removable clamp that mates with the restraining member as the flex circuit is routed first away from the movable member and then routed into the natural rolling bend before the other end of the flex circuit is connected to a stationary component. The restraining member includes an elongated guide portion that routes the flex circuit away from the movable component and a wing-shaped member cantilevered perpendicularly from the end of the elongated guide to route the flex circuit in a direction that allows the flex circuit to naturally bend prior to connection to the stationary component such that the natural bend rolls with the movement of the movable member.
The removable clamp includes a corresponding wing-shaped member that when attached to the restraining member by use of a first clip attaches the removable clamp to the restraining member to restrains the flex circuit through a stressful bend and reroute the flex circuit toward the natural rolling bend.